The present invention relates to an airbag apparatus to be mounted on a vehicle.
An airbag apparatus for protecting an occupant by deploying an airbag in case of emergency such as a collision is mounted on a motor vehicle or the like. For example, an airbag apparatus for a driver's seat is mounted in a steering wheel. An airbag apparatus for a front seat is mounted in front of the front seat.
The airbag apparatus includes a folded airbag, a gas generator for deploying the airbag, and a lid body for covering the airbag. In the case of the airbag apparatus for a front seat, the airbag is stored in a container member, which is referred to as the container or retainer, and a front opening of the container member is covered by the lid body. The lid body of the airbag apparatus for a front seat may be an instrument panel itself, or may be a plate member, which is generally referred to as the lid, cover, deployment door, module cover, and the like, formed separately from the instrument panel. The lid body of the airbag apparatus for a driver's seat is referred to as the module cover in many cases. The lid body is formed of synthetic resin such as polypropylene. The superficial skin of a material such as polyvinyl chloride or thermoplastic polyurethane may be provided in two colors.
Generally, the lid body for the airbag apparatus is formed with a tear line for making the lid body tear when the airbag is deployed. The tear line is, in many cases, constructed of a groove provided on the back surface of the lid body. The tear line may include a center tear line extending laterally with respect to the occupant, and a left tear line and a right tear line continuing from the left and right ends of the center tear line both for the airbag for a driver's seat and the airbag for a front seat.
FIGS. 2, 3, and 4 show constructions of tear lines in the related art. FIG. 2(a) is a front view of a lid for an airbag apparatus for a front seat; FIG. 2(b) is a cross-sectional view taken along the line B—B in FIG. 2(a); FIG. 3 is a front view of a lid having a tear line of a different shape, showing the portion at the center thereof, and FIG. 4 shows the tear line in FIG. 3 in a torn state. FIG. 5 shows the tear line in FIG. 2 in a torn state, and FIG. 6 is a cross sectional view taken along the line VI—VI in FIG. 5.
The tear line on a lid 1 in FIG. 2(a) is constructed in such a manner that intersecting angles cc of a left tear line 3 and a right tear line 4 with respect to a center tear line 2 are right angles. As shown in FIG. 2(b), the tear line is formed by providing a groove on the back surface of the lid 1.
In lid 5 shown in FIG. 3 and FIG. 4, intersecting angles β of a left tear line 7 and a right tear line 8 with respect to a center tear line 6 are obtuse angles (Japanese Utility Model Registration No. 3070586, incorporated by reference herein).
When the airbag is deployed with gas supplied from a gas generator in case of collision of the vehicle, the lids 1, 5 are pushed by the airbags from the backsides, are torn along the tear lines, and open toward the front. When the lids 1, 5 are torn along the center tear lines 2, 6 and the left and the right tear lines 3, 4, 7, 8 as shown in FIGS. 4 and 5, flaps 9, 10 are formed. When these flaps 9, 10 are opened toward the front, openings 11, 12 are formed. The airbags are deployed in front of the occupants to a large extent through the openings 11, 12 and protect the occupants.
As a result of various investigations, when the lid bodies in the related art as shown in FIGS. 2–5 are torn along the tear lines in association with deployment of the airbag, it was found that “hangnails” are generated along the left tear lines and the right tear lines. In other words, as shown in FIG. 6, the lid bodies 1, 5 are torn not only along the tear lines, but the flaps 9, 10 are opened along with the front sides of the adjacent areas, which results in generation of hangnails 9a, 10a like weld flashes on the flaps 9, 10.
Accordingly, there remains a need for a lid body for an airbag apparatus which is torn along tear lines without generating hangnails as described above and an airbag having such lid body.